1. Technical Field
The invention relates to an electric hand-vibration correction method for use in a digital camera or the like, and more particularly, to an electric hand-vibration correction method, an electric hand-vibration correction device, an electric hand-vibration correction program, and an imaging apparatus, which are suitable to embody an electric hand-vibration correction when a picture of the outside of a movable body is taken when a user is on the movable body such as a vehicle, a train, a ship, and an airplane.
2. Description of the Related Art
For example, a user takes a moving picture with holding, in user's hands, a digital camera, a video camera, or the like having a function of taking a moving picture. In this case, if the hands holding the camera vibrate, a position of an image of a still object shown in an image of a certain frame moves in a display screen of the next frame. Thereby, it may be difficult to see the moving picture. Accordingly, there has been provided a method of detecting a hand-vibration vector of an image of a next frame with respect to an image of a certain frame and performing hand-vibration correction so as to prevent the image from vibrating.
FIG. 12 is a diagram illustrating a principle of detecting a movement vector necessary to perform the hand-vibration collection. In this example, each of an image 1 of Nth frame shown in FIG. 12(a) and an image 3 of (N+1)th frame shown in FIG. 12(b) is divided into four segment images, and the following process are performed for each of the segment pictures #1 to #4.
First, an image in a block 2 represented by a predetermined address in the image 1 of the Nth frame shown in FIG. 12(a) is set as a reference image. When an image cut out by a block 4 represented by the same predetermined address in the image 3 of the (N+1)th frame is equivalent to the reference image, the image 3 does not vibrate with respect to the image 1.
However; when the hand-vibration occurs, the reference image in the block 2 is not identical with the image cut out by the block 4. Accordingly, while the block 4 in the image 3 is shifted, in one-pixel unit, to blocks 4a, 4b, 4c, . . . in an X-direction (horizontal direction) and a Y-direction (vertical direction), each of images in the blocks 4a, 4b, 4, . . . is compared with the reference image, thereby acquiring a position of a block cutting a comparison image having the highest corcorrelativity to the reference image.
An operation for acquiring the correlativity is performed by calculating an absolute value of a sum of differences in pixel data (brightness data) in between each pixel of the reference image and those of the comparison images. The comparison image having the minimum absolute value becomes the comparison image having the highest correlativity.
In FIG. 12(b), it is assumed that the comparison image having the highest correlativity with respect to the reference image of the block 2 is cut out from the block 4c. In this case, a difference from the image 1 to the image 3 is a vector “k1.” The vector k1 is a movement vector in the segment picture #1.
Similarly, in the other segment pictures #2 to #4, it is assumed that movement vectors k2 to k4 are calculated, for example. In this case, a simple addition average vector k=[(k1+k2+k3+k4)/4] is a hand-vibration vector between the two pictures.
After the image 1 is displayed, the image 3 is displayed with being shifted in a direction opposite to the hand-vibration vector k (actually, an effective pixel region is widened so that an imaging element can take an image in a region larger than a region of an image to be displayed, and then a cutting-out region of the displayed image, that is, an output region is shifted), the image of the still object in the image 3 overlaps the image of the same still object in the image 1. Therefore, it is possible to display the image without the vibration.
There is JP Sho. 61-201581 A relating to technique for detecting a hand-vibration vector.
The electrically reliable hand-vibration correction can be performed based on the principle described in FIG. 12. However, there is a case where the hand-vibration correction may not be performed, depending on a taken scene. For example, when a picture of the outside scene is taken from a movable body such as a vehicle, an image of a photographic subject moves in the picture as the movable body moves. Accordingly, a large movement vector is calculated in each of the segment pictures shown in FIG. 12. For this reason, it is difficult to extract a small movement vector caused by the hand-vibration or the vibration of the movable body. Thus, it is difficult to perform the hand-vibration correction. Hereinafter, “hand-vibration” is defined to include image blur resulting from the vibration of the movable body.
The invention provides an electric hand-vibration correction method, an electric hand-vibration correction device, an electric hand-vibration correction program, a computer-readable medium storing the program and an imaging apparatus, which are capable of reliably performing an electric hand-vibration correction even if a picture of the outside of a movable body is taken from the movable body.
According to an aspect of the invention, an electric hand-vibration correction method, an electric hand-vibration correction device, an electric hand-vibration correction program divides each of frame images output from an effective pixel region of an imaging element in frame order into a plurality of segment images, calculating a movement vector of each segment image between the frame images, calculating a hand-vibration vector that is a movement vector of each entire frame image, from the movement vectors for the respective segment images, determining an image output region that is cut out from each frame image, based on the hand-vibration vector, and calculating an infinite point based on an intersectional position among the calculated movement vectors of the respective segment images. The image output region is determined using a vibration vector between the infinite points calculated for the respective frame images as the hand-vibration vector.
Also, the image output region may be determined so as to fix positions of the infinite points calculated for the respective frame images.
Also, the image output region may be determined so that positions of the infinite points calculated for the respective frame images always have the same distance from a fixed point in the frame images.
Also, a straight line connecting a infinite point calculated for a certain frame image and a central point of the certain frame image may be calculated. The image output region may be determined based on a component, of the vibration vector between the infinite point calculated for the certain frame image and an infinite point calculated for a next frame image, perpendicular to the straight line with a component, of the vibration vector between the infinite point calculated for the certain frame image and the infinite point calculated for the next frame image, along the straight line being ignored.
Also, the image output region may be determined so as to correct only components having a variation frequency equal to or higher than a predetermined frequency in the vibration vectors calculated in frame order.
According to another aspect of the invention, an imaging apparatus includes an imaging element and any of the electric hand-vibration correction devices set forth above.
According to the invention, the hand-vibration correction is performed using the infinite point. Therefore, it is possible to reliably correct the hand vibration, which occurs even when a picture of the outside of the movable body is taken from the movable body such as a vehicle, a ship, and an airplane.